Add some documentation to DjangoDebug

Author: danpalmer

graphene_django/debug/types.py

@@ -4,4 +4,10 @@
 
 
 class DjangoDebug(ObjectType):
-    sql = List(DjangoDebugSQL)
+    class Meta:
+        description = "Debugging information for the current query."
+
+    sql = List(
+        DjangoDebugSQL,
+        description="Executed SQL queries for this API query.",
+    )